1. Field of the Invention
The present invention relates to a method for saving energy and, in particular, a centralized DC power supply providing DC power to electric appliances and a method for saving power by modulating total or individual power consumption.
2. Description of the Prior Art
Currently, a lighting facility, an electric appliance, or a 3C product needs a specific power supply (with a rectifier/transformer installed internally) which is able to transform 110/220V commercial power to an applicable voltage or DC power for the appliance. In this regard, a manufacturer may provide a power supply with the minimum power rating for a conventional electric appliance by considering manufacturing costs rather than considering power conversion efficiency of the electric appliance.
Therefore, 10˜60% energy loss is created by a conventional electric appliance's power supply and radiated as heat in the course of transforming AC power to DC power. For example, a 60 W power supply with power conversion efficiency of 60% implies 24 W electric power converted to heat, which is dissipated in ambient air and results in not only senseless repetitive energy loss or waste but also creates burden for an air conditioner system, which consumes additional electric power to take heat away.
In a power supply control system of a conventional lighting facility, each lighting unit needs a specific power supply, each of which causes the above-noted energy loss and is additionally provided with a dimmer unit for dimming the single lighting unit. For simultaneous dimming of more than one lighting unit, a dimmer control circuit should be designed in the dimmer unit of each lighting unit. However, a conventional dimming approach consuming electricity to reduce illumination of a lighting unit still fails to reduce total power consumption and generate energy savings.
As shown in FIG. 4A, three 40 W, 50 W and 60 W lamps 8 as lighting facilities linking an AC power unit 81 consume full power, that is, 40+50+60=150 W.
As shown in FIG. 4B, LED lamps 7 as alternative lighting facilities comprise rectifiers/transformers 71, which are held in the LED lamps 7 or installed additionally and have the same functions of conventional lamps 8 (FIG. 4A), consuming full power of 150 W while turned on simultaneously.
In summary, conventional lighting facilities have the following drawbacks:
1. A specific power supply working with each lighting unit has a lower power rating, a low Power Factor (PF) and poor power conversion efficiency which contribute to power consumption costs;
2. Specific power supplies working with all lighting units result in repetitive energy losses during power conversion, which contribute to power consumption costs;
3. Identical dimmer units installed in all lighting units for dimming increase acquisition costs; and
4. An approach based on resistances to consume electric power and reduce illumination of a lighting unit increases electricity expenses because the total power consumption remains the same.
Accordingly, the inventor, considering various drawbacks derived from conventional methods, created and developed a centralized DC power supply system and a method for economically controlling power consumption, after years of research.